CVE-2026-77486 in SQL Server
Summary
by MITRE • 09/09/2026
Integer overflow or wraparound in SQL Server allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a critical security flaw within Microsoft SQL Server, specifically involving an integer overflow or wraparound condition that can be exploited remotely by an unauthenticated attacker. This type of defect typically arises when the application performs arithmetic operations on data values without adequately validating whether the result will exceed the maximum limit supported by the underlying variable type. In the context of network-facing services like database engines, such miscalculations often occur during the processing of specially crafted packets or queries sent over the network interface. When an integer overflow occurs in memory management routines, it can lead to incorrect buffer size calculations, causing the system to allocate insufficient memory for a specific operation while subsequently writing data that exceeds this allocated boundary. This discrepancy results in a heap-based buffer overflow, where excess data spills into adjacent areas of memory, potentially overwriting critical control structures such as return addresses or function pointers.
From an operational perspective, the impact of this vulnerability is severe because it allows for arbitrary code execution with the privileges of the SQL Server service account. If the database engine is configured to run under a high-privilege system account, which was common in older configurations and still possible in some legacy environments, successful exploitation grants the attacker full control over the underlying operating system. This level of access enables the installation of malware, the creation of new administrative accounts for persistent backdoor access, or the modification and deletion of data within the database itself. Furthermore, because SQL Server is a core component in many enterprise infrastructure architectures, compromising this service can serve as an initial foothold for lateral movement across the network, allowing attackers to pivot from the compromised database server to other critical systems such as file servers, application servers, or domain controllers.
The technical nature of this flaw aligns with CWE-190, which defines integer overflow or wraparound errors that occur when arithmetic operations produce a result too large for the data type used to store it. In many cases involving SQL Server network protocols, these vulnerabilities are also associated with CWE-787, an out-of-bounds write condition resulting from improper boundary checks on input values derived from external sources. The exploitation vector is classified under MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques, as the attacker leverages the memory corruption to execute arbitrary commands within the context of the database process. Additionally, if the vulnerability allows for remote code execution without user interaction or authentication, it falls under the Remote Code Execution (RCE) category in ATT&CK T1203, highlighting its potential for automated worm-like propagation across vulnerable networks.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is to apply the latest security patches provided by Microsoft as soon as they are available, ensuring that all instances of SQL Server running in production environments are updated to versions where this integer handling logic has been corrected with proper bounds checking. Organizations should also enforce strict network segmentation policies to limit exposure; database servers should not be directly accessible from untrusted networks such as the public internet and should instead reside within a secure internal subnet behind firewalls that restrict inbound traffic to specific management IPs or application tiers only. Furthermore, adhering to the principle of least privilege is essential by configuring SQL Server services to run under low-privilege domain accounts rather than local system administrators, thereby limiting the potential damage even if exploitation occurs. Regular vulnerability scanning and penetration testing focused on database-facing interfaces can help identify misconfigurations or unpatched instances before they are exploited in the wild.